Calibration approach for camera placement

ABSTRACT

Multiple cameras are used for tool positioning, as-built documentation, and/or personnel monitoring in construction site. A camera unit comprises one or more imaging devices, a processing computer, and a communication device. The camera units are placed at multiple locations in a construction site to cover an area. The camera units are self-positioned by detecting a calibration target that moves within a working volume. The camera units can detect and calculate positions of objects, including measurement sticks, tools, personnel, etc., in the area.

CROSS-REFERENCE TO RELATED APPLICATIONS

The following four U.S. patent applications (including this one) arebeing filed concurrently, and the entire disclosure of the otherapplications are incorporated by reference into this application for allpurposes:

-   -   application Ser. No. 15/604,169, filed May 24, 2017, entitled        “Infrastructure Positioning Camera System”;    -   application Ser. No. 15/604,161, filed May 24, 2017, entitled        “Calibration Approach for Camera Placement”; and    -   application Ser. No. 15/604,172, filed May 24, 2017, entitled        “Measurement, Layout, Marking, Firestop Stick.”

BACKGROUND

This disclosure relates to systems and methods that facilitatepositioning points and objects in a workspace or at a worksite, such asfor example at a construction site. When the interior of a building isbeing finished, connectors, anchors, and the like are attached to thefloors, ceilings and other structures in the building and cuts are madeand holes drilled using power saws and drills. All of this must beaccomplished using special power tools at predetermined locations,requiring that the tools be operated at numerous precisely definedpositions in the building. For example, nail guns, power saws, powderanchor tools, and the like are used to nail, cut, install fasteners, andperform other operations at predetermined points within the buildingwith little error. In any building, a large number of electrical,plumbing, and HVAC components must be properly sited and installed,usually with power tools. Additionally, finishing a building interioralso requires that a number of different tools that are not powered beoperated at precisely defined positions, such as for examplereinforcement bar scanners. Positioning both power tools and non-powertools must be accomplished quickly and with some precision with respectto the surrounding walls, ceilings and floors as they are roughed in.Typically, it has required a significant amount of labor to lay outvarious construction points at such a construction site. Teams ofworkers have been needed to measure and mark predetermined locations. Itwill be appreciated that this process has been subject to errors,resulting from measurement mistakes and from accumulated errors.Further, the cost of this layout process and the time needed to performthe layout process have both been significant.

Various location determining systems, including systems that incorporateone or more robotic total stations, have been used for building layout.The total station in such a system, positioned at a fixed, knownlocation, directs a beam of laser light at a retro-reflective target. Asthe target moves, robotics in the total station cause the beam of lightto track the target. By measuring the time of travel of the beam fromthe total station to the retro-reflective target and then back to thetotal station, the distance to the target is determined. The directionalorientation of the beam to the target is also measured. Since thedimensional coordinates of the total station are known, the dimensionalcoordinates of the retro-reflective target can easily be determined.Based on the measured position of the retro-reflective target, and thedesired position of some building feature, such as a drilled hole, or afastener, the operator can move the reflector to the desired position,and mark the position.

Although position determination systems, such as ranging radio systemsand robotic total station systems, can facilitate and speed the layoutprocess, nevertheless the layout process has continued to be lengthy,tedious, and expensive. Previous applications have been filed addressingsystems and/or methods to reduce construction expense and/or labor. Forexample, U.S. patent application Ser. No. 13/800,350, filed Mar. 13,2013, which is incorporated by reference, provides systems and methodsfor positioning a tool in a workspace.

BRIEF SUMMARY

In some embodiments, a system for tool positioning, as-builtdocumentation, personnel monitoring in construction site using cameranetwork is described. The system comprises multiple camera units, a mainprocessing computer, measurement stick(s), calibration target(s), anduser visualization devices. A camera unit comprises one or more imagingdevices, a processing computer, and/or a communication device.

Camera units are placed at multiple unknown locations in a constructionsite that cover a working volume. The camera units are self-positionedin an arbitrary coordinate system by detecting a calibration target thatmoves within the working volume by one or more human operators. Then thearbitrary coordinate system can be transformed to a desired coordinatesystem.

Camera units, in combination with a main processing computer, can detectand calculate positions of objects in the working volume, includingmeasurement sticks, tools, personnel, etc. Camera units in combinationwith the main processing computer can monitor work progress for as-builtdocumentation and reporting. The measurement stick can measure a pointand/or a distance within the working volume.

In some embodiments, a camera unit can detect its own motion bycontinuously monitoring a static scene. For example, if the camera unitremains stationary, the scene from the camera unit is also stationary,except moving objects such as workers and etc. If the camera unit moves,then all objects in the scene will move. In some embodiments, a cameraunit detecting its own motion reduces or prevents object position errorscaused by unintentional movement of the camera unit.

In some embodiments, a camera system comprises a housing; a firstimaging system integrated with the housing, the first imaging systemcomprising: a first lens, and a first image sensor for detecting lightfrom the first lens to generate first data, wherein: the first data isimage data, and the first imaging system has a first field of view; asecond imaging system integrated with the housing, the second imagingsystem comprising: a second lens, and a second image sensor fordetecting light from the second lens to generate second data, wherein:the second data is image data, the second imaging system has a secondfield of view, the first field of view and the second field of viewcombine to form a third field of view, the third field of view is largerthan the first field of view, and the third field of view is larger thanthe second field of view; a processor, integrated with the housing,configured to generate third data from the first data and/or the seconddata, wherein the third data corresponds to position information of anobject; and a communication interface configured to transmit the thirddata. In some embodiments, the housing is a first housing of a firstcamera unit; the processor is a first processor; and the camera systemfurther comprises: a second housing of a second camera unit, the secondhousing comprising: a third imaging system, a fourth imaging system, anda second processor to generate fourth data from image data from thethird imaging system and/or the fourth imaging system; and a mainprocessing computer configured to: receive the third data and the fourthdata, and determine a position of the object in three dimensions basedthe third data and the fourth data. The second processor, the thirdimaging system, and/or the fourth imaging system are configured toreceive power from a power source integrated with the first housing. Thefirst field of view is between 20 degrees and 40 degrees, the secondfield of view is between 20 degrees and 40 degrees, and a fourth fieldof view of imaging systems integrated with the housing is 90 degrees,plus or minus 30 degrees. In some embodiments, imaging systemsintegrated with the housing have a combined field of view of 180degrees, plus or minus 30 degrees. In some embodiments the systemfurther comprises a third housing, and two or more imaging systemsintegrated with the third housing, such that imaging systems of thefirst housing, imaging systems integrated with the second housing, andimaging systems integrated with the third housing are configured to havea combined field of view of 270 degrees, plus or minus 30 degrees;and/or a third imaging system integrated with the housing, the thirdimaging system comprising: a third lens; and a third image sensor fordetecting light from the third lens, wherein: the third imaging systemhas a fourth field of view, the fourth field of view partially overlapswith the third field of view to form a fifth field of view, and thefifth field of view is 90 degrees plus or minus 30 degrees. In someembodiments, the fifth field of view is 90 degrees, plus or minus 10degrees; the third data is based on the first data and the second data;and/or the housing is a first housing of a first camera unit, the camerasystem further comprises a second camera unit removably connected withthe first camera unit, the first camera unit has a field of view of 90degrees, +/−30 degrees, and the second camera unit has a field of viewof 90 degrees, +/−30 degrees, such that the first camera unit and thesecond camera unit have a combined field of view of 180 degrees, +/−30degrees. In some embodiments, the system further comprises a magnetcoupled with the housing to attach the housing to metal; and or a powerinterface integrated with the housing to connect to a power source usinga power cord, and a battery integrated with the housing.

In some embodiments, a method for using a camera system comprisesacquiring a first image of an object using a first image sensor, whereinthe first image is defined by first data; acquiring a second image ofthe object using a second image sensor, wherein: the second image isdefined by second data, and the first image sensor and the second imagesensor are both within a housing of a camera unit; calculating thirddata by processing the first data and/or the second data, wherein: thethird data corresponds to position information of the object in relationto the first image sensor, the third data corresponds to positioninformation of the object in relation to the second image sensor, andcalculating the third data is performed by a processor within thehousing of the camera unit; and transmitting the third data from theprocessor within the housing of the camera unit to a main processingcomputer, wherein the main processing computer is outside the housing ofthe camera unit. The housing of the camera unit is a first housing of afirst camera unit, the processor is a first processor, and the methodfurther comprises placing the first housing of the first camera unit ata first location; placing a second housing of a second camera unit at asecond location, wherein: the second camera unit comprises a third imagesensor and a second processor, the first location is separated from thesecond location by at least 10 feet and less than 200 feet; acquiring athird image using the third image sensor; calculating fourth data basedon the third image; transmitting the fourth data from the secondprocessor to the main processing computer; and calculating athree-dimensional position of the object based on the third data andfourth data. In some embodiments the method comprises trackingpersonnel, in three dimensions based at least partially on the firstdata and the second data; recording images from the camera unit tocreate a time-lapse sequence to show construction progress for as-builtdocumentation; and/or removably connecting a third camera unit and afourth camera unit with the first camera unit and the second cameraunit, such that first camera unit, the second camera unit, the thirdcamera unit, and the fourth camera unit have a combined field of view of360 degrees. The camera unit is a first camera unit and the methodfurther comprises removably connecting the first camera unit with asecond camera unit, such that first camera unit and the second cameraunit have a combined field of view of 180 degrees, +/−30 degrees. Insome embodiments, a memory device comprises instruction that whenexecuted cause one or more processors to perform one or more steps.

In some embodiments, a method for calibrating a camera system comprisesplacing a first camera unit in an area; placing a second camera unit inthe area; acquiring, using the first camera unit, a first sequence ofimages of a target moving in the area; acquiring, using the secondcamera unit, a second sequence of images of the target moving in thearea, wherein images of the first sequence of images are related by timeto images of the second sequence of images; calculating a position andan orientation of the second camera unit relative to the first cameraunit based on the first sequence of images of the target and the secondsequence of images of the target; identifying two or more points in thein the first sequence of images and in the second sequence of images,wherein the two or more points correspond to points in a model; andcalculating a position and an orientation of the first camera unitrelative to the model based on identification of the two or more pointsin the first sequence of images and in the second sequence of images. Insome embodiments, the method comprises moving the target in the area;recalculating the position and/or the orientation of the first cameraunit based on detecting movement of the first camera unit, wherein: theposition and/or the orientation of the first camera unit is recalculatedafter calculating the position and the orientation of the second cameraunit relative to the first camera unit, and the position and/or theorientation of the first camera unit is recalculated based on detectinga background shift using images acquired by the first camera unit;displaying to a user the number of calculated positions of the target asthe calculated positions are made; displaying to a user calculatedpositions of the target from one or more image sensors in one or morecamera units; and/or transmitting positions and/or orientations ofobjects to a display, wherein the display is a monitor; and/or part of ahand-held device, a head-mount device, a helmet-mount device, orglasses. In some embodiments calculating a position and orientation ofthe first camera unit relative to the model is performed aftercalculating a position and an orientation of the second camera unitrelative to the first camera unit; the target is a first target, thefirst sequence of images and the second sequence of images includeimages of a second target, and the method further comprises calculatingthe position and the orientation of the second camera unit relative tothe first camera unit further based on the first sequence of images ofthe second target and the second sequence of images of the secondtarget; a number of calculated positions of the target used incalculating the position and the orientation of the second camera unitrelative to the first camera unit is between 100 and 10,000, and thenumber of calculated positions correspond to a number of frames used inthe first sequence of images and the number of frames used in the secondsequence of images used to calculate the position and the orientation ofthe second camera unit relative to the first camera unit; and/ordisplaying to the user the number of calculated positions of the targetchanges in color and/or style based on the number of calculatedpositions. In some embodiments, a memory device causes one or moreprocessors to perform one or more steps.

In some embodiments, a system for calibrating camera units comprises afirst camera unit; a second camera unit; a target; and one or moreprocessors configured to: acquire a first sequence of images of thetarget using the first camera unit, acquire a second sequence of imagesof the target using the second camera unit, wherein images of the firstsequence of images are related in time to images of the second sequenceof images, and calculate a relative position of the second camera unitin relation to the first camera unit based on the first sequence ofimages of the target and the second sequence of images of the target. Insome embodiments, the system further comprises a third camera unitconfigured to acquire a third sequence of images of the target; a fourthcamera unit configured to acquire a fourth sequence of images of thetarget; and the one or more processors are configured to: calculate aposition and an orientation of the third camera unit with respect to thefirst camera unit based on the first sequence of images of the targetand the third sequence of images of the target, and calculate a positionand an orientation of the fourth camera unit with respect to the firstcamera unit based on the first sequence of images of the target and thefourth sequence of images of the target; and/or a display configured todisplay positions and/or orientations of objects to a user. In someembodiments, the one or more processors are further configured to:identify two or more points in the first sequence of images and in thesecond sequence of images, wherein the two or more points correspond topoints in a model, and calculate a position and an orientation of thefirst camera unit relative to the model based on the first sequence ofimages of the target, the second sequence of images of the target, andidentification of the two or more points in the first sequence of imagesand/or in the second sequence of images; the first camera unit comprisesthree image sensors; the target is a stick with markings; and/or the oneor more processors are configured to: identify two or more points in anarea on the first sequence of images and/or on the second sequence ofimages, wherein the two or more points correspond to points in a modelof the area, and calculate a position and an orientation of the firstcamera unit in relation to the model based on identifying the two ormore points in the first sequence of images and/or in the secondsequence of images.

In some embodiments, a system for providing position and orientation ofan object at a worksite comprises a first camera unit; a second cameraunit; a third camera unit; a device, wherein the device comprisesmarkings of known dimensions; and one or more processors configured totrack a position and an orientation of the device in three dimensionsbased on the known dimensions of the markings and known positions of thefirst camera unit, the second camera unit, and the third camera unit. Insome embodiments, the system comprises a fourth camera unit; a chip setfor coordinating timing of the first camera unit, the second cameraunit, and the third camera unit in acquiring images; and/or a first setof templates for determining a scale to use for selecting a template ofa second set of templates, and the second set of templates foridentifying an end of the device. In some embodiments, the device is astick, the stick comprising central markings and end markings, and thecentral markings are used to determine a scale of the stick in imagesand the end markings are used to determine an end of the stick inimages; and/or the one or more processors are configured to track aposition and an orientation of the device in three dimensions based onthe known dimensions of the markings and known positions of the firstcamera unit, the second camera unit and the third camera unit by:acquiring a plurality of images of the object using the first cameraunit, the second camera unit, and the third camera unit, wherein theobject has a first end and a second end; calculating a plurality oftwo-dimensional line equations based on the plurality of images;calculating a three-dimensional line equation based on the plurality oftwo-dimensional line equations; determining the first end and/or thesecond end of the object in each of the plurality of images; anddetermining coordinates of the object in three dimensions based ondetermining the first end and/or the second end of the object in theplurality of images. In some embodiments, the one or more processors areconfigured to calculating the plurality of two-dimensional lineequations by:

converting color images to gray tone, applying a derivative filter togray-tome images, subtracting background in images, detecting key pointsto identify the object in images, and refining an initial line equationbased on detecting the key points; the device is a stick, and the stickcomprises: a first end, a second end opposite the first end, a firstmarking nearer the first end than the second end for imaging by thefirst camera unit and the second camera unit, and a second markingbetween the first marking and the second end for imaging by the firstcamera unit and the second camera unit; the stick has a length equal toor greater than 0.5 meters and equal to or less than 1.5 meters; and/oreach template of the first set of templates has a width, and the widthis equal to or greater than one pixel and equal to or less than 20pixels.

In some embodiments, a method for providing position and orientation ofan object at a worksite comprises acquiring three or more images of theobject using three or more imaging devices, wherein the object comprisesmarkings of known dimensions; calculating a plurality of two-dimensionalline equations from the three or more images; calculating athree-dimensional line equation from the plurality of two-dimensionalline equations; determining a first point and/or a second point on theobject in the three or more images based on the three-dimensional lineequation and the known dimensions of the markings; and determiningcoordinates of the object in three dimensions using the first pointand/or the second point of the object in the three or more images. Insome embodiments, calculating the plurality of two-dimensional lineequations comprises: converting color images of the three or more imagesto gray tone, applying a derivative filter to the three or more images,subtracting background from the three or more images, detecting keypoints to identify the object, and refining an initial line equation;calculating the three-dimensional line equation comprises: generatingplane coordinates of multiple planes based on the two-dimensional lineequations, determining an intersection of the multiple planes in threedimensions, checking for residual two-dimensional line equations, anddetermining a final three-dimensional line equation; and/or determiningthe first point and/or the second point comprises: projecting athree-dimensional line equations onto each image of the three or moreimages, extracting pixels under the three-dimensional line equationprojected onto each image, matching a line image with a predefinedtemplate, and acquiring the first point and/or the second point on thethree or more images. In some embodiments, a memory device comprisesinstructions that cause one or more processors to perform one or moresteps.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described in conjunction with the appendedfigures.

FIG. 1 depicts a simplified drawing of an embodiment of a camera systemwith a measurement stick.

FIG. 2 depicts a simplified drawing of an embodiment of a configurationof camera units at a worksite.

FIG. 3 depicts a simplified perspective drawing of an embodiment ofcamera units placed in a worksite.

FIG. 4 depicts example images with marked points on the images of acalibration target moved by an operator.

FIG. 5 depicts a simplified perspective drawing of example measurementstick applications.

FIG. 6 depicts a simplified perspective drawing of an example of ameasurement stick used for layout and/or marking a location on a floor.

FIG. 7 depicts a simplified perspective drawing of an example ofmeasurement sticks used for point measurements for quality checkdocumentation.

FIG. 8 depicts a simplified perspective drawing of an example of ameasurement stick for placing firestop.

FIG. 9 depicts a simplified perspective drawing of an example of ameasurement stick used for direct fastening.

FIG. 10 depicts a simplified perspective drawing of an example of directfastening on pan decking.

FIG. 11 depicts a simplified perspective drawing of an example ofdrilling or direct fastening on a ceiling while a user is on a scissorlift.

FIG. 12 depicts a simplified perspective drawing of an example of cameraunits used for personnel monitoring for safety and security.

FIG. 13A illustrates a flowchart of an embodiment of a process forcalculating coordinates of the measurement stick in three dimensions.

FIG. 13B depicts a simplified drawing of an embodiment of a stick.

FIG. 14 illustrates a flowchart of an embodiment of a process forcalculating a 2D line equation from each image.

FIG. 15 depicts a simplified drawing of the collinearity condition.

FIG. 16 illustrates a flowchart of an embodiment of a process forcalculating a three-dimensional line equation.

FIG. 17A illustrates a flowchart of an embodiment of a process fordetermining an endpoint, in two dimensions, of a measurement stick.

FIG. 17B depicts a simplified drawing of an embodiment of a subset of afirst set of templates.

FIG. 17C depicts a simplified drawing of an embodiment of a subset of asecond set of templates.

FIG. 18 illustrates a flowchart of an embodiment of a process fordetermining coordinates of the measurement stick in three dimensions.

FIG. 19 illustrates the concept of space intersection.

FIG. 20 illustrates the concept of space intersection for a multiplecamera case.

FIG. 21 illustrates a simplified diagram of an embodiment of a cameraunit.

FIG. 22 illustrates a flowchart of an embodiment of a process forcalculating positions and orientations of cameras without surveying.

FIG. 23 illustrates a flowchart of an embodiment of a process for usinga camera system.

FIG. 24 depicts a block diagram of an embodiment of a computer system.

FIG. 25 depicts a block diagram of an embodiment of a special-purposecomputer system.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

The ensuing description provides preferred exemplary embodiment(s) only,and is not intended to limit the scope, applicability, or configurationof the disclosure. Rather, the ensuing description of the preferredexemplary embodiment(s) will provide those skilled in the art with anenabling description for implementing a preferred exemplary embodiment.It is understood that various changes may be made in the function andarrangement of elements without departing from the spirit and scope asset forth in the appended claims.

While an interior of a building is being finished, connectors, anchors,and the like are attached to the floors, ceilings, and other structuresin the building. Further, cuts are made and holes drilled using powersaws and drills. Tools, such as special power tools, are used atpredetermined locations, such that the tools are operated at numerous,precisely-defined positions in the building. For example, nail guns,power saws, powder anchor tools, and the like are used to nail, cut,install fasteners, and perform other operations at predetermined pointswithin the building with little error. In many buildings, a large numberof electrical, plumbing, and HVAC components are sited and installed,usually with power tools. Additionally, finishing a building interioralso uses a number of different tools that are not powered, which arealso operated at precisely defined positions, such as for examplereinforcement bar scanners. Positioning both power tools and non-powertools quickly and with precision (e.g., with respect to surroundingwalls, ceilings, and floors) can save time and reduce constructioncosts. A significant amount of labor is used to lay out variousconstruction points at such a construction site. Teams of workers havebeen used to measure and mark predetermined locations. It will beappreciated that this process has been subject to errors, resulting frommeasurement mistakes and from accumulated errors. Further, the costusing teams of workers to complete a layout process, and the time neededto perform the layout process, have both been significant.

Various location determining systems, including systems that incorporateone or more robotic total stations, have been used for building layout.The total station in such a system, positioned at a fixed, knownlocation, directs a beam of laser light at a retro-reflective target. Asthe target moves, robotics in the total station cause the beam of lightto track the target. By measuring the time of travel of the beam fromthe total station to the retro-reflective target and then back to thetotal station, the distance to the target is determined. The directionalorientation of the beam to the target is also measured. Sincedimensional coordinates of the total station are known, the dimensionalcoordinates of the retro-reflective target can easily be determined.Based on the measured position of the retro-reflective target, and thedesired position of some building feature, such as a drilled hole, or afastener, the operator can move the reflector to the desired position,and mark the position. Although position determination systems, such asranging radio systems and robotic total station systems, can facilitateand speed the layout process, the layout process has continued to belengthy, tedious, and expensive. In some embodiments, systems and/ormethods are described to speed up, reduce manual labor, and/or reduceexpense of construction.

System Configuration

Referring first to FIG. 1, a simplified drawing of an embodiment of acamera system with a measurement stick 104 is shown. The camera systemcomprises camera units 108, a main processing computer, the measurementstick 104, and/or a calibration target. The camera system comprisesthree or more camera units 108. In some embodiments, the camera systemcomprises two or more measurement sticks 104, two or more calibrationtargets, and/or two or more main processing computers.

Each camera unit 108 comprises a processor unit, a communication device,and one or more imaging devices 112. The imaging devices 112 each have aposition and/or orientation that is known relative to other imagingdevices 112 that are part of a camera unit 108. The imaging devices 112acquire image sequences. The processor unit in the camera unit 108processes the image sequences. The communication device transmits andreceives data with the main processing computer.

In FIG. 2, a simplified drawing of an embodiment of a configuration ofcamera units 108 at a worksite is shown. An operator attaches cameraunits 108 to a column, wall, etc. A position of the camera unit 108 isnot surveyed. The operator can add or subtract camera units 108depending on a size of the worksite and/or a position of the camera unit108.

Each camera unit 108 has a field of view (FoV). In some embodiments, theFoV of a camera unit 108 is 90 degrees+/−2%, 5%, 10%, 15%, and/or 20%.Two camera units 108 are combined for a 180 degree FoV. Three cameraunits 108 are combined for a 270 degree FoV. Four camera units 108 arecombined for a 360 degree FoV. In some embodiments, each camera unit 108has a FoV equal to 30, 36, 40, 45, 51, 60, 72, 180, 270, or 360degrees+/−5%, 10%, and/or 15%. An operator can put two camera units 108together to cover 180 degrees and four camera units 108 for 360 degrees.In some embodiments, camera units 108 are removably connected to eachother (e.g., to have a combined field of view). In some embodiments,camera units 108 are removably connected to each other using pressurefit, interlocking parts, magnets, hook and loop, and/or snaps.

FIG. 3 depicts a simplified perspective drawing of an embodiment ofcamera units 108 placed in a worksite. The operator attaches the cameraunits 108 to a column 304, wall 308, ceiling 312, floor 316, truss 320,etc. Camera units 108, which are modular, allow for quick setup. In someembodiments, no surveying of camera unit 108 locations is used.

Rapid deployment camera (camera positioning)

In FIG. 4, example images with marked points on the images of acalibration target 404 moved by an operator is shown. In someembodiments, one or more operators walk around the worksite withcalibration targets 404. The camera units 108 detect (e.g.,automatically) the calibration target 404 (e.g., in real-time). Thecamera units 108 in combination with the main processing computercalculate positions and orientations of imaging devices 112 of cameraunits 108 while removing (e.g., automatically) outliers. In someembodiments, a bundle adjustment technique with RANSAC (random sampleconsensus) is used. The “235” on the figure is a number counting howmany points have been used to determine relative positions of the cameraunits 108. In the figure, there have been two-hundred, thirty-fivepositions of the target's position in three dimensions were calculatedand used for determining relative positions of the camera units 108.

Positions and/or orientations of camera units 108 are calculated basedon the marked points. However, there are sometimes false results (whichare not the calibration target 404) because of lighting condition,occlusion, and etc. Thus, in some embodiments, false-detection resultsof the marked points are removed before calculating the positions and/ororientations of the camera units 108. To remove a false-detectionresult, a pair of camera units 108 identifies inliers (which are correctdetections of the calibration target 404) among marked points by fittingto a relative orientation model using a RANSAC algorithm. Inliers aremarked points of the calibrated target using the camera units 108,wherein the positions and/or orientations of the pair of camera units108 is in an arbitrary coordinate system. Inliers are identified usingother pairs of camera units 108. Inliers from one pair of camera units108 are matched to inliers from another pair of camera units 108. Abundle adjustment with a RANSAC algorithm is run using matched inliersand positions and/or orientations of the camera units 108, wherein thearbitrary coordinate system is used as initial values. In someembodiments, similar features are matched in image sequences to aBuilding Information Model (BIM) to calculate positions and/ororientations of the camera units 108. In some embodiments, the similarfeatures are distinct.

Measurement Stick

FIG. 5 depicts a simplified perspective drawing of an example ofmeasurement stick 104 applications. Accurate 3D position of a tip 504 ofthe measurement stick 104 in real-time can be made. To measure a point,an operator holds the measurement stick 104 for a few seconds. Multiplemeasurement sticks 104 can work at same time.

The measurement stick 104 can be used for layout/marking location on thefloor 316 (FIG. 6), point measurement for quality check documentation(FIG. 7), firestop placement by attaching a dispenser 804 to themeasurement stick 104 (FIG. 8), direct fastening by attaching a directfastener 904 to the measurement stick 104 (FIG. 9), and etc.

In some embodiments, the measurement stick 104 has a black and whitestripe pattern so that the measurement stick 104 is recognizable bycamera units 108 and/or the main processing computer. The camera unit108 detects distinct points on the measurement stick 104 and then fitsthe points to a line.

An orientation of the measurement stick 104 is determined from linescalculated by each camera unit 108. A perspective center of an imagingdevice 112 and a line on an image plane of the imaging device 112provides a plane. The orientation of the measurement stick 104 iscalculated by an intersection of planes from the imaging devices 112.Since a length of the measurement stick 104 is known, once one end pointof the measurement stick 104 is detected, the system can calculate a 3Dposition of the tip 504 of the measurement stick.

Tool Tracking

FIG. 10 depicts a simplified perspective drawing of an example of directfastening on Pan-Decking. FIG. 11 depicts a simplified perspectivedrawing of an example of drilling or direct fastening on a ceiling whilea user is on a scissor lift. The main computer processor is capable offinding and tracking various tools 1004 (e.g., construction tools).System memory may include data defining a digital image and/ordimensions of each of a plurality of tools 1004 so that the maincomputer processor can distinguish between the plurality of tools 1004used. In some embodiments, a position and/or orientation of a tool 1004is determined based on a recognition of an overall three-dimensionalimage of the tool 1004 and/or on certain features of the tool 1004. Insome embodiments, certain features of the tool 1004 are added to thetool 1004 for a purpose of determining the position and/or orientationof the tool 1004. In some embodiments, certain features of the tool 1004are built into the tool 1004 for a purpose other than for determiningthe position and/or orientation of the tool 1004.

Personnel Monitoring

FIG. 12 depicts a simplified perspective drawing of an example of cameraunits used for personnel monitoring for safety and security. In someembodiments, the main computer processor is configured to identify andtrack people. Thus camera units 108 can be used as a surveillance systemfor safety and/or security. For example, an alarm could sound if aperson entered a safety-alert zone; or a user of a tool could be alertedthat another person is within an unsafe distance of the tool. In someembodiments, camera units 108 acquire images throughout the day to forma history of images. The history of images can be used for trackingwork, verifying work is completed, and/or logging events to video (e.g.,for quality control, paying contractors, security, etc.). In someembodiments, daily and/or hourly documentation is recorded.

Self-realigning Camera

In some embodiments, unintentional and/or intentional movement of acamera unit 108 can be detected. Calculated values of positions and/ororientations of camera units 108 are important for accurate positioningof objects. However, camera units 108 can be moved for various reasons(such as a worker or tool accidentally bumps the camera unit 108). Amoving object can be differentiated from a background in an imagesequence. If a camera unit 108 remains stationary, then the backgroundremains stationary in the image sequence. If a camera unit 108 moves,then all objects, including the background, moves. If the background isdetermined to have moved, whether or not a camera unit 108 has moved canbe tested by comparing distinct features from previously recorded imagesand compare to a current image of the camera unit 108. If the positionof the camera unit 108 has changed, then the position and/or orientationof the camera unit 108 (and possibly other camera units 108) will berecalculated (e.g., using distinct features that have 3D coordinates; orusing a calibration target). In some embodiments, 3D coordinates ofdistinct features are calculated during after initial calibration of thecamera units 108.

Measurement Stick Detection

Referring next to FIG. 13, a flowchart of an embodiment of a process1300 for calculating coordinates of the measurement stick in threedimensions is shown. Process 1300 begins in step 1304 with calculating atwo-dimensional line equation from each image of a plurality of images(e.g., two or more images or three or more images). The plurality ofimages are acquired by a plurality of imaging devices 112 (e.g., two ormore imaging devices 112 or three or more imaging devices 112) in aplurality of camera units 108 (e.g., in two or more camera units 108 orin three or more camera units 108). In step 1308, a three-dimensionalline equation is calculated based on the two-dimensional line equations.An endpoint of the measurement stick 104 is determined based on thethree-dimensional line equation and at least one image of the pluralityof images, step 1312. In step 1316, coordinates of the measurement stick104 are determined in three dimensions based on determining the endpointin the at least one image. Further details to steps 1304, 1308, 1312,and 1316 are provided below.

FIG. 13B depicts a simplified drawing of an embodiment of a stick 1320(e.g., to be used as the measurement stick 104). The stick 1320 is anelongated device defined by a length, D, and a width (e.g., a diameter;the width being between greater than 0.5 cm and less than 18 cm; lengthD is greater than 0.25 meters and less than 4 meters and/or length D isequal to or greater than 0.5 meters and equal to or less than 1.5meters). The stick 1320 comprises a first end 1324-1 and a second end1324-2. The first end 1324-1 is separated from the second end 1324-2 bythe length D. The stick 1320 comprises first markings, central markings1328, and second markings, end markings 1332.

The central markings 1328 comprise a plurality of high contrast regions.In the embodiment shown, the central markings 1328 comprise alternatingwhite regions and black regions. In some embodiments a repeating patternis used. The black regions of the central markings 1328 each have afirst span S-1 (e.g., a first length). The end markings 1332 have asecond span S-2 (e.g., a second length). The second span is differentfrom the first span S-1. The white regions of the central markings 1328have a third span S-3 (e.g., a third length). In some embodiments, thethird span S-3 is equal to the first span S-1. In some embodiments,there is a first end marking 1332-1 and a second end marking 1332-2. Thefirst end-marking is the first span S-1 and the second end marking1332-2 has a fourth span S-4 (e.g., a fourth length). In someembodiments S-4=S-1. In some embodiments, S-4 is not equal to S-1 and/orS-4 is a different color than S-1 to differentiate between the first end1324-1 of the stick 1320 and the second end 1324-2 of the stick 1320.

FIG. 14 illustrates a flowchart of an embodiment of a process forcalculating the 2D line equation from an image. The process forcalculating the 2D line equation from each image begins in step 1404with changing a color image to a gray image (or obtaining a gray image).For example, a red/green/blue (RGB) image is converted to a gray-toneimage. In some embodiments, a Gaussian filter is applied afterconverting the image to the gray-tone image (e.g., to reduce noise).

In step 1408 a derivative filter is applied to the gray-tone image toproduce a derivative image. In some embodiments, the derivative filteris a Laplacian filter. In the derivative image, edges are easier toidentify. Edges are areas where pixel values change rapidly (sometimesreferred to as “corners”).

A background is subtracted, step 1412, to produce a foreground image.For example, a background is subtracted from the derivative image toidentify a foreground area. The foreground area is a part of an imagethat has a moving object (e.g., stick 1320). There can be more than oneforeground area of the foreground image (e.g., for two targets, a firstforeground area with the first target is not contiguous with a secondforeground area of the image with the second target). In someembodiments, a median filter is applied to the foreground image. In someembodiments, the median filter is applied to reduce sparsely occurringwhite and black pixels (salt-and-pepper noise).

In step 1416, key points are detected to identify the stick 1320. Insome embodiments, a FAST (Features from Accelerated Segment Test)algorithm, such as detectFASTFeatures in MATLAB (9.1; R2016b), is usedfor edge detection. Black regions and white regions of the centralmarkings 1328 on the stick 1320 are detected as key points. Key pointsare fitted to an initial line equation. In some embodiments, RANSAC isused to fit key points to the initial line equation because RANSACdiscards outliers.

In some embodiments, the initial line equation is optionally refined,step 1420. For example, if the stick 1320 is too close to an imagingdevice 112, the initial line equation might be a little inaccurate. Insome embodiments, to refine the initial line equation, black and whitestripe areas (e.g., images of black regions and white regions of thecentral markings 1328) on the gray image are identified by: using theinitial line equation, identifying quad shapes (e.g., one quad shape perblack region or white region of the central markings 1328) near theinitial line equation, and calculating average and/or standard deviationof pixel values inside the quad shapes to find stripes. Centroids of thequad shapes, which are determined to be images of central markings 1328,are calculated. For example, centroids are fit to a line using RANSAC tocalculate the 2D line equation. The 2D line equation in each image ofthe plurality of images is calculated, if the 2D line equation exists.

In step 1308 of FIG. 13, a three-dimensional line equation iscalculated. In some embodiments a collinearity condition, sometimesreferred to as collinearity equations, is used in calculating thethree-dimensional line equation. FIG. 15 depicts a simplified drawing ofthe collinearity condition. The collinearity condition represents ageometric relationship wherein a point (A) in an object space, an imageof the point (a) on an image plane 1504, and a perspective center (L) ofthe image plane 1504 are on a straight line in three-dimensional space.

The collinearity condition can be expressed by the following equations:

$x_{a} = {{x_{o} - {f\lbrack \frac{{m_{11}( {X_{A} - X_{L}} )} + {m_{12}( {Y_{A} - Y_{L}} )} + {m_{13}( {Z_{A} - Z_{L}} )}}{{m_{31}( {X_{A} - X_{L}} )} + {m_{32}( {Y_{A} - Y_{L}} )} + {m_{33}( {Z_{A} - Z_{L}} )}} \rbrack}} = {x_{o} - {f\frac{r}{q}}}}$$y_{a} = {{y_{o} - {f\lbrack \frac{{m_{21}( {X_{A} - X_{L}} )} + {m_{22}( {Y_{A} - Y_{L}} )} + {m_{23}( {Z_{A} - Z_{L}} )}}{{m_{31}( {X_{A} - X_{L}} )} + {m_{32}( {Y_{A} - Y_{L}} )} + {m_{33}( {Z_{A} - Z_{L}} )}} \rbrack}} = {y_{o} - {f\frac{s}{q}}}}$

In the above equations, x_(a) and y_(a) are coordinates of the image ofthe point (a) (sometimes referred to as photo coordinates); x_(o) andy_(o) are coordinates of the principal point (the principal point is thepoint on the image plane 1504 onto which the perspective center (L) isprojected); f is a focal length of a camera (e.g., of an imaging device112); X_(L), Y_(L), and Z_(L) are object space coordinates of theperspective center L; X_(A), Y_(A), and Z_(A) are object spacecoordinates of point A; and the m's are functions of the three rotationangles (ω, φ, and κ) such that:m ₁₁=cos φ cos κm ₁₂=sin ω sin φ cos κ+cos ω sin κm ₁₃=−cos ω sin φ cos κ+sin ω sin κm ₂₁=cos φ cos κm ₂₂=−sin ω sin φ cos κ+cos ω sin κm ₂₃=cos ω sin φ cos κ+sin ω sin κm ₃₁=sin φm ₃₂=−sin ω cos φm ₃₃=cos ω cos φ

Since the collinearity equations are nonlinear, the linearized forms ofthe equations are used to iteratively solve many photogrammetricsolutions. The collinearity equations can be linearized by usingTaylor's theorem. In this manner, the collinearity equations can bewritten as follows (simplified):J=b ₁₁ dω+b ₁₂ dφ+b ₁₃ dκ−b ₁₄ dX _(L) −b ₁₅ dY _(L) −b ₁₆ dZ _(L) +b ₁₄dX _(A) +b ₁₅ dY _(A) +b ₁₆ dZ _(A) +e _(x) _(o)K=b ₂₁ dω+b ₂₂ dφ+b ₂₃ dκ−b ₂₄ dX _(L) −b ₂₅ dY _(L) −b ₂₆ dZ _(L) +b ₂₄dX _(A) +b ₂₅ dY _(A) +b ₂₆ dZ _(A) +e _(y) _(o)

FIG. 16 illustrates a flowchart of an embodiment of a process forcalculating the three-dimensional line equation (step 1308 of FIG. 13).For each 2D line equation, plane coordinates are generated. Planecoordinates are generated by determining a plane defined by the 2D lineequation and the perspective center L of an imaging device that acquiredan image that the 2D line equation is based on.

In step 1608, an intersection of multiple planes is determined. Planecoordinates of multiple planes (e.g., from multiple cameras) arecalculated in object space. The intersection of the multiple planesdetermines an initial 3D line equation. The initial 3D line equation isan equation of a line in object space (thus the initial 3D line equationis an equation of a line in three-dimensional space). In someembodiments, the initial line equation is used as the 3D line equation.

In step 1612, residual 2D line equations are checked to find wrong 2Dline equations. Residual 2D line equations are determined by planesformed from 2D line equations that fail to intersect with two or moreother planes and/or fail to intersect within a certain tolerance of theinitial 3D line equation (e.g., within 0.5, 0.25, 0.1, or 0.07 meters ofthe initial line equation; and/or two or more sticks 1320 are notoperated within 0.5 meters of each other). For example, a first cameraunit 108-1, a second camera unit 108-2, a third camera unit 108-3, and afourth camera unit 108-4 are used to acquire images of the stick 1320.The first camera unit 108-1, the second camera unit 108-2, the thirdcamera unit 108-3, and the fourth camera unit 108-4 are time synced toacquire images at the same time. The first camera unit 108-1, the secondcamera unit 108-2, and the third camera unit 108-3 each calculate two 2Dline equations in an image. The fourth camera unit 108-4 calculatesthree 2D line equations in an image. Plane coordinates are calculated,and two initial 3D line equations are determined based on intersectingplanes. Though the plane formed by a third 2D line equation from thefourth camera unit 108-4 intersects with planes formed with 2D lineequations from other camera units 108, there is not an intersection ofat least three planes corresponding to the third 2D line equation of thefourth camera unit 108-4; thus the third 2D line equation is thrown outas an error. The system determines that there are two sticks 1320 beingobserved based on determining two 3D line equations. In someembodiments, three or more camera units 108 are used to observe an areaso that two or more measuring sticks 1320 can be used within the areaand residual 2D line equations can be identified and removed. If onlytwo camera units 108 are used, it is difficult to identify and removeresidual 2D line equations because two planes formed by two 2D lineequations will usually intersect, even if one of the two 2D lines areresidual.

In step 1616, the final 3D line equation is determined. For example, afirst intersection of a first plane corresponding to the first cameraunit 108-1 and a second plane corresponding to the second camera unit108-2 is close to, but does not perfectly overlap (e.g., within 0.1 or0.05 meter of each other), a second intersection of the first plane anda third plane corresponding to the third camera unit 108-3. Similarly, athird intersection of the second plane and the third plane may notperfectly overlap the first intersection or the second intersection, butbe close defined by the certain tolerance (e.g., within 0.1 meters ofeach other). In some embodiments, the first intersection, the secondintersection, and the third intersection are averaged to determine thefinal 3D line equation (e.g., having removed outlying intersections instep 1612). In some embodiments, a rolling tolerance is used. Forexample, if three later measurements are within the tolerance (e.g.,0.05 meters) of measurement being determined, then the measurement beingdetermined is used.

In some embodiments, the method further comprises displaying to a user anumber of calculated positions of the target as the calculated positionsare made. Displaying to the user the number of calculated positions ofthe target changes in color and/or style based on the number ofcalculated positions. In some embodiments, the method further comprisesdisplaying to a user calculated positions and/or orientations of atarget. In some embodiments, the display is a monitor; and/or part of ahand-held device, a head-mount device, a helmet-mount device, orglasses.

FIG. 17A illustrates a flowchart of an embodiment of a process fordetermining an endpoint of the measurement stick 104 in an image (step1312 of FIG. 13). In some embodiments, the endpoint is determined in twoor more images and/or from two or more imaging devices. In someembodiments, both endpoints of the measurement stick 104 are determined.In step 1704, the final 3D line equation is projected back into animage-coordinate system (e.g., using the collinearity equations). Thus aprojected line is formed on the image. The projected line matchesclosely (e.g., within a given tolerance) to the 2D line equation in theimage. In some embodiments, if the projected line does not match closeto the 2D line equation in an image (e.g., within a given tolerance),then that image is not used. In some embodiments, the 2D line equationand the 3D line equation have undetermined lengths (e.g., they areequations of lines that can extend to infinity).

In step 1708, pixel values are extracted under the projected final 3Dline on the image to make a line image. The pixel values of the lineimage, over some length) are alternating dark and light values. In someembodiments, the line image has a 1 pixel height and can vary in length.

The line image is matched with a first set of templates 1720, step 1712,to determine a scale. The first set of templates are 1 pixel in heightand have stripe patterns to fit to the central markings 1328. In someembodiments, each template of the first set of templates has a heightequal to or greater than one pixel and equal to or less than 50, 25, 20,15, 10, or 5 pixels. FIG. 17B provides a simplified drawing of anembodiment of a subset of the first set of templates 1720. The subset ofthe first set of templates comprises a first central template 1724-1, asecond central template 1724-2, and a third central template 1724-3. Thecentral templates 1724 have a height, H. Each central template 1724corresponds to a different scale. In some embodiments, the height, H, isone pixel. The line image is compared the central templates 1724 andmatched with one of the central templates 1724. The central markings1328 of the stick 1320 are known dimensions. A scale of the stick 1320is determined based matching a central template 1724 to the line imageof the stick 1320.

In step 1716, an endpoint on the image is acquired. FIG. 17C depicts asimplified drawing of an embodiment of a second set of templates 1730.The second set of templates comprises a plurality of end templates 1734.The end 1324 of the stick 1320 is identified in the image by selectingan end template 1734 of similar scale as the central template 1724. Forexample, a first end template 1734-1 is of similar scale to the firstcentral template 1724-1; a second end template 1734-2 is of similarscale to the second central template 1724-2; and a third end template1734-3 is of similar scale to the third central template 1724-3.

The end template 1734 that is selected is then compared to the lineimage to identify an end marking 1332 from the line image. The endmarking 1332 is of known dimensions so that the end 1324 of the stick1320 can be determined based on the end template 1734 compared to theline image. In some embodiments, the end templates 1734 are 1 pixel inheight. In some embodiments, two endpoints are acquired. In someembodiments, two ends 1324 of the stick 1320 have different patterns(and in some embodiments use different end templates), thus whichendpoint corresponds to which end 1324 can be determined. In someembodiments, a point, other than an endpoint, is determined. Forexample, instead of a determining the first endpoint and/or the secondendpoint, a first point and/or a second point are determined. In someembodiments, the first end point is a point that is closer to the firstend 1324-1 than the second end 1324-2, not necessarily an image of thefirst end 1324-1.

FIG. 18 illustrates a flowchart of an embodiment of a process fordetermining coordinates of the measurement stick in three dimensions(step 1316 of FIG. 13). In step 1804 a line per image is generatedconnecting an endpoint in object space and the camera's perspectivecenter in object space. In step 1808, an intersection of multiple linesis used to calculate an endpoint in world frame (e.g., using SpaceIntersection below). One or two endpoints of the measurement stick 104are then acquired in three dimensions of the object space. In someembodiments, the 3D line equation is used mapping the endpoint from oneimage onto the 3D line equation.

Space Intersection. Space intersection is the photogrammetric processthat estimates 3D coordinates of a point in the object space from photocoordinates observations in a stereo pair. FIG. 19 illustrates theconcept of space intersection. Known values are the exterior orientationparameters of two photographs (L₁, L₂), photo coordinates of a point(a₁, a₂) in each photograph, and initial value for the point in objectspace (A). In some embodiments, the initial value for the point inobject space (A) is determined by calculating a first vector starting atthe perspective center of the first camera and to photo coordinates of apoint on an image plane of the first camera; calculate a second vectorfor the second camera (e.g., starting at a perspective center of thesecond camera to a point on an image plane of the second camera);calculating an intersection of the first vector and the second vector,and if an intersection does not exist, finding a point near (e.g.,closest point between) the first vector and the second vector.

The following equations shows the linearized form of the collinearityequations for space intersection. Since the exterior orientationparameters of each photograph are known, the object coordinate terms(dX_(A), dY_(A), dZ_(A)) are estimated iteratively in the linearizedform of the collinearity condition equation.J=b ₁₄ dX _(A) +b ₁₅ dY _(A) +b ₁₆ dZ _(A) +e _(x) _(a)K=b ₂₄ dX _(A) +b ₂₅ dY _(A) +b ₂₆ dZ _(A) +e _(y) _(a)

The following equation shows the matrix form of the previous equations.Subscripts C0 and C1 represent cameras 0 and 1 (or photographs 0 and 1),respectively. The solution of the equation can be estimated iterativelyusing Least-square solution.

$\begin{bmatrix}(J)_{c_{0}} \\(K)_{c_{0}} \\(J)_{c_{1}} \\(K)_{c_{1}}\end{bmatrix} = {{\begin{bmatrix}( b_{14} )_{c_{0}} & ( b_{15} )_{c_{0}} & ( b_{16} )_{c_{0}} \\( b_{24} )_{c_{0}} & ( b_{25} )_{c_{0}} & ( b_{26} )_{c_{0}} \\( b_{14} )_{c_{1}} & ( b_{15} )_{c_{1}} & ( b_{16} )_{c_{1}} \\( b_{24} )_{c_{1}} & ( b_{25} )_{c_{1}} & ( b_{26} )_{c_{1}}\end{bmatrix}\begin{bmatrix}{dX}_{A} \\{dY}_{A} \\{dZ}_{A}\end{bmatrix}} + e}$

The following table shows the iterative space intersection algorithm.

Data: photo coordinate observations: (x_(a), y_(a))c₀, (x_(a), y_(a))c₁Initial values of point A: (X_(A), Y_(A), Z_(A)) While (∥{circumflexover (ξ)}∥>threshold) Calculate design and y matrix:$A = \;\begin{bmatrix}( b_{14} )_{c_{0}} & ( b_{15} )_{c_{0}} & ( b_{16} )_{c_{0}} \\( b_{24} )_{c_{0}} & ( b_{25} )_{c_{0}} & ( b_{26} )_{c_{0}} \\( b_{14} )_{c_{1}} & ( b_{15} )_{c_{1}} & ( b_{16} )_{c_{1}} \\( b_{24} )_{c_{1}} & ( b_{25} )_{c_{1}} & ( b_{26} )_{c_{1}}\end{bmatrix}$ $y = \begin{bmatrix}(J)_{c_{0}} \\(K)_{c_{0}} \\(J)_{c_{1}} \\(K)_{c_{1}}\end{bmatrix}$ Estimate parameter matrix: $\hat{\xi} = {\begin{bmatrix}{dX}_{A} \\{dY}_{A} \\{dZ}_{A}\end{bmatrix} = {( {A^{T}A} )^{- 1}A^{T}y}}$ Updatesolutions: $\begin{bmatrix}X_{A} \\Y_{A} \\Z_{A}\end{bmatrix} = {\begin{bmatrix}X_{A} \\Y_{A} \\Z_{A}\end{bmatrix} + \begin{bmatrix}{dX}_{A} \\{dY}_{A} \\{dZ}_{A}\end{bmatrix}}$ End Result: 3D object space coordinates of point A

Space intersection with multiple cameras. The bundle adjustmenttechnique can be used to solve for the space intersection solution inthe multiple camera case. FIG. 20 illustrates the concept of spaceintersection for the multiple camera case. Known values are the exteriororientation parameters of the cameras or photographs (L₁, L₂, L₃, andL₄), the photo coordinates of a point (a₁, a₂, a₃, and a₄), and theinitial value for the point in object space (A) is a center of theobject space.

The following equation shows matrix form of space intersection equationfor the multiple camera case. In this equation, subscripts C₀, C₁, C₂and C₃ represent cameras 0, 1, 2, and 3, respectively. Solution ofequation can be estimated iteratively by using least-squares solution.The sizes of the design matrix and the observation matrix are 2n×3 and2n×1, respectively; where n is the number of cameras (or photographs).

$\begin{bmatrix}(J)_{c_{0}} \\(K)_{c_{0}} \\(J)_{c_{1}} \\(K)_{c_{1}} \\(J)_{c_{2}} \\(K)_{c_{2}} \\(J)_{c_{3}} \\(K)_{c_{3}}\end{bmatrix} = {{\begin{bmatrix}( b_{14} )_{c_{0}} & ( b_{15} )_{c_{0}} & ( b_{16} )_{c_{0}} \\( b_{24} )_{c_{0}} & ( b_{25} )_{c_{0}} & ( b_{26} )_{c_{0}} \\( b_{14} )_{c_{1}} & ( b_{15} )_{c_{1}} & ( b_{16} )_{c_{1}} \\( b_{24} )_{c_{1}} & ( b_{25} )_{c_{1}} & ( b_{26} )_{c_{1}} \\( b_{14} )_{c_{2}} & ( b_{15} )_{c_{2}} & ( b_{16} )_{c_{2}} \\( b_{24} )_{c_{2}} & ( b_{25} )_{c_{2}} & ( b_{26} )_{c_{2}} \\( b_{14} )_{c_{3}} & ( b_{15} )_{c_{3}} & ( b_{16} )_{c_{3}} \\( b_{24} )_{c_{3}} & ( b_{25} )_{c_{3}} & ( b_{26} )_{c_{3}}\end{bmatrix}\begin{bmatrix}{dX}_{A} \\{dY}_{A} \\{dZ}_{A}\end{bmatrix}} + e}$

Referring next to FIG. 21, a simplified diagram of an embodiment of acamera unit 108 is shown. The camera unit 108 comprises a housing 2102,one or more imaging devices 112, a processor unit 2104, and acommunication device 2108. In some embodiments, the camera unit 108lacks a user input and/or a display screen. The processor unit 2104 is aspecialized processing unit and not a general-purpose computer. In someembodiments, the camera unit 108 comprises one or more input/output(I/O) ports 2112. In some embodiments, the I/O ports 2112 are arrangedto connect (e.g., a direct connection) to neighboring camera units 108.In some embodiments, the I/O port 2112 is configured for a wiredconnection (e.g., for connection to another camera unit 108, to a hub,and/or to a central processing computer). In some embodiments, the I/Oports 2112 are part of the communication device 2108.

The communication device 2108 transmits and/or receives data withanother camera unit 108 and/or a central processing computer. In someembodiments, the communication device 2108 comprises an antenna forwireless communication.

In the embodiment shown, the camera unit 108 comprises three imagingdevices 112 integrated in the housing 2102. A first imaging device112-1, a second imaging device 112-2, and a third imaging device 112-3.Each imaging device comprises a lens 2116 and an image sensor 2120. Theimage sensor 2120 is separated from the lens 2116 by a distance equal tothe focal length f of the lens 2116.

The first imaging device 112-1 has a first field of view 2124-1. Thesecond imaging device 112-2 has a second field of view 2124-2. The thirdimaging device 112-3 has a third field of view 2124-3. The first fieldof view 2124-1 and the second field of view 2124-2 at least partiallyoverlap, but not totally overlap, forming a fourth field of view 2124-4.The fourth field of view 2124-4 is greater than the first field of view2124-1. The fourth field of view 2124-4 is greater than the second fieldof view 2124-2.

Each imaging device 2116 has an orientation defined by a vector normalto the lens 2116 (e.g., pointing “out,” away from the image sensor2120). The orientation of the first imaging device 112-1 is at −30degrees from the orientation of the second imaging device 112-2. Theorientation of the third imaging device 112-3 is at +30 degrees from theorientation of the second imaging device 112-2.

The camera unit 108 has a fifth field of view 2124-5. The fifth field ofview 2124-4 is equal to a sum of the first field of view 2124-1, thesecond field of view 2124-2, and the third field of view 2124-3.

In some embodiments, the housing comprises two or more cameras. In someembodiments, the housing comprises a processor to process images fromthe two or more cameras locally. Thus data generated by processing theimages, which is much smaller than image data, is transmitted from thecamera unit to the main processing computer. In some embodiments, cameraunits 108 each comprise a chipset for time synchronization. Thus imagesfrom sensors 2120 of different camera units 108 can by synced, enablingthe main processing computer to identify position and/or orientation ofan object in three dimensions. In some embodiments, images are processedat 30 frames a second (e.g., +/−30, 20, 10, and/or 5%). In someembodiments, camera units are used to track the object (e.g., at lessthan 30, 20, 10, and/or 1 frame per second (e.g., to reducecomputations). In some embodiments, the camera units 108 track theobject in a first mode and then determine position of the object in asecond mode.

In some embodiments, a camera unit 108 comprises a power source (e.g., abattery, a solar panel, or both a battery and a solar panel). In someembodiments, the camera unit 108 comprises a connector to a powersource. For example, the camera unit 108 comprises a USB port to connectto a USB power source and/or to download and/or upload data; the cameraunit could comprise a port to connect to an outlet (e.g., a wall outletthat uses 120 volt alternating current). In some embodiments, the cameraunit 108 comprises both a battery and a port to connect to power. Forexample, a camera unit 108 could use a battery while a central powersource is unavailable. In a further example, a camera unit 108 on apillar that has an outlet could be plugged into the outlet and anothercamera unit

In some embodiments, a camera unit 108 is considered a main unit and hasa power source and/or a port to connect to power and/or a transmitter totransmit data; another camera unit 108 is considered an axially unit andlacks a power source, a port to connect to power, a processor, and/or atransmitter (e.g., to enable less costly manufacturing). An auxiliaryunit could with a main unit during operation. For example, for a 360degree field of view, four camera units 108, each with 90 degree fieldof views are coupled together; one of the four camera units 108 is amain unit and three of the four camera units 108 are auxiliary units.Other variations can be used, for example, each camera unit 108comprises a battery, a USB port, and a port for external power, but whenplugging in camera units 108, one camera unit 108, the main unit, isplugged into external power (e.g., a wall outlet) and other camera units108 (auxiliary units) are powered by plugging into the main unit. Insome embodiments, the auxiliary units transmit data (e.g., through awired USB port and/or wirelessly such as through Bluetooth) to the mainunit and the main unit transmits data to the main processing computer.Transmitting data wirelessly close takes less power than transmittingdata farther from the transmission point. Thus the main unit could beplugged in and the auxiliary units using battery power and/or the mainunit having a larger battery than the auxiliary units.

In some embodiments, the camera units 108 are configured to be mounted.In some embodiments, the camera unit 108 is removably attached duringuse. In some embodiments, the camera unit 108 comprises a magnet 2126coupled with the housing. Thus the camera unit 108 could be placed on apiece of metal (e.g., a wall, a support beam, a stationary vehicle, apole, a sign, a filing cabinet, a door, a tripod, etc.). In someembodiments, a magnet 2126 is used because a magnet on metal is easy toput up and less likely to rotate. In some embodiments, the camera unit108 comprises a clamp (e.g., a claim is attached to the housing and isused to grip an I-beam). In some embodiments, the camera is hung (e.g.,using a cord, rope, or fishing line). In some embodiments, fasteners(e.g., screws, nails, and/or bolts, are used). For example, the housingcomprises eyelets. In some embodiments, the housing comprises threads(e.g., ¼×20 inch threads for mounting to a tripod bolt).

In some embodiments, camera units 108 are separated from each other byat least 10, 15, 20, and/or 30 feet and/or less than 500, 300, 200, 100,50, and/or 30 feet. For example, camera units 108 are separated fromeach other by at least 10 feet and no more than 50 feet. In someembodiments, camera separation is limited because cameras separated bygreater distance can help triangulate better but if distances become toolarge then objects on the image sensors can become too small, dependingon a field of view of the imaging devices. Applicant has found thatthree imaging devices in one housing is a good balance between the fieldof view of each imaging device and application to indoor workspaces.

FIG. 22 illustrates a flowchart of an embodiment of a process 2200 forcalculating positions and orientations of cameras without surveying. Theprocess 2200 begins in step 2204 by placing a first camera in an area(e.g., the working volume) and a second camera in the area. In someembodiments, the first camera is part of a first camera unit 108-1 andthe second camera is part of a second camera unit 108-2. In someembodiments, the first camera and/or the second camera is an imagingdevice 112.

In step 2208, a target is moved through the area. In some embodiments,the target is the measurement stick 104. In some embodiments, the targetis rotated and/or made to revolve about an axis as the target is movedthrough the area. The measurement stick 104 is defined by a length and aradius. In some embodiments, the axis is perpendicular to the length ofthe measurement stick 104. In some embodiments, the axis is at themiddle of the length of the measurement stick 104.

In step 2212, a first sequence of images of the target is acquired usingthe first camera and a second sequence of images of the target isacquired using the second camera. In some embodiments, the first cameraand the second camera are linked (e.g., wired and/or wireless; toacquire images concurrently).

In step 2216, positions and/or orientations of the first camera and/orthe second camera are calculated. The calculations of the positionsand/or orientations of the first camera and/or the second camera arebased on the first sequence of images of the target, the second sequenceof images of the target, and identification of the two or more points inthe area in the first sequence of images and/or on the second sequenceof images. In some embodiments, the calculations of the positions and/ororientations of the first camera and/or the second camera are based onthe first sequence and the second sequence of images by using thecollinearity equations and image acquisition of the measurement stick todetermine relative positions and orientations of the first camera to thesecond camera (e.g., using techniques discussed above). The relativepositions are determined in an arbitrary coordinate system. Usingmultiple images (e.g., at least 40 images) and multiple positions of themeasurement stick reduces errors and enables more accurate determinationof relative positions. In some embodiments 100, 200, 300, or more (andless than 500, 1000, and/or 10,000) positions of a target are used toget good relative position measurements. For example, 250, 300, 350,400, or 500 positions of the target are used. In some embodiments,positions are redundant. For example, if the target is held stationaryfor a half second, and the camera speed is 30 frames per second, thenthere would be 15 images from each camera that could be redundant. Insome embodiments, a user or a robot moves about the area twirling themeasurement stick 104 so that the measurement stick 104 is in manydifferent positions and orientations (e.g., to increase accuracy ofdetermining relative positions of the first camera and the secondcamera).

In some embodiments, work can be performed in the arbitrary coordinatesystem (e.g., building a shed). In some embodiments, the positionsand/or orientations of the first camera and/or the second camera arebased on the identification of two or more points in the area by usingthe two or more points to calculate the position and/or orientation ofthe first camera and/or the second camera in relation to the area. Forexample, a user positions the measurement stick 104 at a pointidentified on the model of the area. In another example, the firstcamera uses the two or more points to determine the first camera'sposition and orientation in relation to the model of the area (sometimesreferred to as the model coordinate system or world system). Thearbitrary system is then mapped to the model coordinate system to thatother cameras' positions and orientations can be calculated in the modelcoordinate system). In some embodiments, three, four, or more camerasare used and/or calibrated to each other. For example a third cameraand/or a fourth camera are placed in the area and acquire a thirdsequence and/or a fourth sequence of images of the target. The target isidentified by each camera at the same time. In some embodiments, tocalculate each cameras' position and orientation more precisely, anumber of identified targets is important; the more the better. In someembodiments, results for the second camera, the third camera, and so onare calculated with respect to the first camera. For example, the firstcamera has three-dimensional coordinates (e.g., Cartesian XYZcoordinates) and three angles (e.g., for orientation in threedimensions) are [0, 0, 0, 0, 0, 0]. In some embodiments, an axis (e.g.,the X axis or Y axis) is defined by a line between the first camera andthe second camera. Three angles and YZ (or XZ) are then calculated forthe second camera. Angles and position coordinates (e.g., XYZ) are thencalculated for additional cameras, if additional cameras are used. Insome embodiments, two angles are used to define an orientation of acamera.

In step 2220, two or more points are identified in the area on one ormore images of the first sequence of images and/or on one or more imagesof the second sequence of images. The two or more points correspond topoints in a model of the area (e.g., a CAD model). The two or morepoints are used to calculate a position and/or orientation of the firstcamera and/or the second camera to the model. In some embodiments, themeasurement stick is placed at the two or more points to identify thetwo or more points to the camera units. In some embodiments, step 2220is skipped and camera positions and orientations are calculated relativeto each other and not to a model.

FIG. 23 illustrates a flowchart of an embodiment of a process 2300 forusing a camera system. The process 2300 begins in step 2304 withacquiring a first image and a second image of an object. The first imageis acquired using a first image sensor (e.g., using the image sensor2120 of the first imaging device 112-1). The first image is defined byfirst data. The second image is acquired using a second image sensor(e.g., using the image sensor 2120 of the second imaging device 112-2).The second image is defined by second data. The first image sensor andthe second image sensor are both within a housing of a camera unit 108(e.g., both within the housing 2102).

In step 2308, third data is calculated based on the first image and thesecond image. The processor unit 2104 processes the first data and thesecond data to calculate the third data. The third data corresponds toposition information of the object in relation to the first image sensorand to position information of the object in relation to the secondimage sensor. In some embodiments, the position information includes aphoto coordinate a of the object on the first image sensor and/or aphoto coordinate a of the object on the second image sensor.

In step 2312, the third data, which is based on the first data and thesecond data, is transmitted. The third data is transmitted (e.g., usingcommunication device 2108) from the processor unit 2104, which is in thehousing 2102, to a main processing computer. The main processingcomputer is outside the housing 2102 of the camera unit 108. Byprocessing information at the processor unit 2104 (e.g., locally) lessdata is transmitted on a network, saving bandwidth on the network.

In some embodiments a first camera unit 108-1 is placed at a firstlocation and a second camera unit 108-2 is placed at a second location.In some embodiments, the first location is separated from the secondlocation by at least 10 feet and less than 200 feet.

Referring next to FIG. 24, an exemplary environment with whichembodiments may be implemented is shown with a computer system 2400 thatcan be used by a designer 2404 to design, for example, electronicdesigns. The computer system 2400 can include a computer 2402, keyboard2422, a network router 2412, a printer 2408, and a monitor 2406. Themonitor 2406, processor 2402 and keyboard 2422 are part of a computersystem, which can be a laptop computer, desktop computer, handheldcomputer, mainframe computer, etc. The monitor 2406 can be a CRT, flatscreen, etc.

A designer 2404 can input commands into the computer 2402 using variousinput devices, such as a mouse, keyboard 2422, track ball, touch screen,etc. If the computer system 2400 comprises a mainframe, a designer 2404can access the computer 2402 using, for example, a terminal or terminalinterface. Additionally, the computer 2402 may be connected to a printer2408 and a server 2410 using a network router 2412, which may connect tothe Internet 2418 or a WAN.

The server 2410 may, for example, be used to store additional softwareprograms and data. In one embodiment, software implementing the systemsand methods described herein can be stored on a storage medium in theserver 2410. Thus, the software can be run from the storage medium inthe server 2410. In another embodiment, software implementing thesystems and methods described herein can be stored on a storage mediumin the computer 2402. Thus, the software can be run from the storagemedium in the computer 2402. Therefore, in this embodiment, the softwarecan be used whether or not computer 2402 is connected to network router2412. Printer 2408 may be connected directly to computer 2402, in whichcase, the computer system 2400 can print whether or not it is connectedto network router 2412.

With reference to FIG. 25, an embodiment of a special-purpose computersystem 2500 is shown. The above methods may be implemented bycomputer-program products that direct a computer system to perform theactions of the above-described methods and components. Each suchcomputer-program product may comprise sets of instructions (codes)embodied on a computer-readable medium that directs the processor of acomputer system to perform corresponding actions. The instructions maybe configured to run in sequential order, or in parallel (such as underdifferent processing threads), or in a combination thereof. Afterloading the computer-program products on a general purpose computersystem, it is transformed into the special-purpose computer system 2500.

Special-purpose computer system 2500 comprises a computer 2402, amonitor 2406 coupled to computer 2402, one or more additional useroutput devices 2530 (optional) coupled to computer 2402, one or moreuser input devices 2540 (e.g., keyboard, mouse, track ball, touchscreen) coupled to computer 2402, an optional communications interface2550 coupled to computer 2402, a computer-program product 2505 stored ina tangible computer-readable memory in computer 2402. Computer-programproduct 2505 directs system 2500 to perform the above-described methods.Computer 2402 may include one or more processors 2560 that communicatewith a number of peripheral devices via a bus subsystem 2590. Theseperipheral devices may include user output device(s) 2530, user inputdevice(s) 2540, communications interface 2550, and a storage subsystem,such as random access memory (RAM) 2570 and non-volatile storage drive2580 (e.g., disk drive, optical drive, solid state drive), which areforms of tangible computer-readable memory.

Computer-program product 2505 may be stored in non-volatile storagedrive 2580 or another computer-readable medium accessible to computer2402 and loaded into memory 2570. Each processor 2560 may comprise amicroprocessor, such as a microprocessor from Intel® or Advanced MicroDevices, Inc.®, or the like. To support computer-program product 2505,the computer 2402 runs an operating system that handles thecommunications of product 2505 with the above-noted components, as wellas the communications between the above-noted components in support ofthe computer-program product 2505. Exemplary operating systems includeWindows® or the like from Microsoft Corporation, Solaris® from SunMicrosystems, LINUX, UNIX, and the like.

User input devices 2540 include all possible types of devices andmechanisms to input information to computer 2402. These may include akeyboard, a keypad, a mouse, a scanner, a digital drawing pad, a touchscreen incorporated into the display, audio input devices such as voicerecognition systems, microphones, and other types of input devices. Invarious embodiments, user input devices 2540 are typically embodied as acomputer mouse, a trackball, a track pad, a joystick, wireless remote, adrawing tablet, a voice command system. User input devices 2540typically allow a user to select objects, icons, text and the like thatappear on the monitor 2406 via a command such as a click of a button orthe like. User output devices 2530 include all possible types of devicesand mechanisms to output information from computer 2402. These mayinclude a display (e.g., monitor 2406), printers, non-visual displayssuch as audio output devices, etc.

Communications interface 2550 provides an interface to othercommunication networks and devices and may serve as an interface toreceive data from and transmit data to other systems, WANs and/or theInternet 2418. Embodiments of communications interface 2550 typicallyinclude an Ethernet card, a modem (telephone, satellite, cable, ISDN), a(asynchronous) digital subscriber line (DSL) unit, a FireWire®interface, a USB® interface, a wireless network adapter, and the like.For example, communications interface 2550 may be coupled to a computernetwork, to a FireWire® bus, or the like. In other embodiments,communications interface 2550 may be physically integrated on themotherboard of computer 2402, and/or may be a software program, or thelike.

RAM 2570 and non-volatile storage drive 2580 are examples of tangiblecomputer-readable media configured to store data such ascomputer-program product embodiments, including executable computercode, human-readable code, or the like. Other types of tangiblecomputer-readable media include floppy disks, removable hard disks,optical storage media such as CD-ROMs, DVDs, bar codes, semiconductormemories such as flash memories, read-only-memories (ROMs),battery-backed volatile memories, networked storage devices, and thelike. RAM 2570 and non-volatile storage drive 2580 may be configured tostore the basic programming and data constructs that provide thefunctionality of various embodiments.

Software instruction sets that provide functionality may be stored inRAM 2570 and non-volatile storage drive 2580. These instruction sets orcode may be executed by the processor(s) 2560. RAM 2570 and non-volatilestorage drive 2580 may also provide a repository to store data and datastructures. RAM 2570 and non-volatile storage drive 2580 may include anumber of memories including a main random access memory (RAM) to storeof instructions and data during program execution and a read-only memory(ROM) in which fixed instructions are stored. RAM 2570 and non-volatilestorage drive 2580 may include a file storage subsystem providingpersistent (non-volatile) storage of program and/or data files. RAM 2570and non-volatile storage drive 2580 may also include removable storagesystems, such as removable flash memory.

Bus subsystem 2590 provides a mechanism to allow the various componentsand subsystems of computer 2402 communicate with each other as intended.Although bus subsystem 2590 is shown schematically as a single bus,alternative embodiments of the bus subsystem 2590 may utilize multiplebusses or communication paths within the computer 2402.

Specific details are given in the above description to provide athorough understanding of the embodiments. However, it is understoodthat the embodiments may be practiced without these specific details.For example, circuits may be shown in block diagrams in order not toobscure the embodiments in unnecessary detail. In other instances,well-known circuits, processes, algorithms, structures, and techniquesmay be shown without unnecessary detail in order to avoid obscuring theembodiments.

Implementation of the techniques, blocks, steps and means describedabove may be done in various ways. For example, these techniques,blocks, steps and means may be implemented in hardware, software, or acombination thereof. For a hardware implementation, the processing unitsmay be implemented within one or more application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described above, and/or a combination thereof.

Also, it is noted that the embodiments may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination corresponds to a return of the functionto the calling function or the main function.

Furthermore, embodiments may be implemented by hardware, software,scripting languages, firmware, middleware, microcode, hardwaredescription languages, and/or any combination thereof. When implementedin software, firmware, middleware, scripting language, and/or microcode,the program code or code segments to perform the necessary tasks may bestored in a machine readable medium such as a storage medium. A codesegment or machine-executable instruction may represent a procedure, afunction, a subprogram, a program, a routine, a subroutine, a module, asoftware package, a script, a class, or any combination of instructions,data structures, and/or program statements. A code segment may becoupled to another code segment or a hardware circuit by passing and/orreceiving information, data, arguments, parameters, and/or memorycontents. Information, arguments, parameters, data, etc. may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory. Memory may be implemented within the processor orexternal to the processor. As used herein the term “memory” refers toany type of long term, short term, volatile, nonvolatile, or otherstorage medium and is not to be limited to any particular type of memoryor number of memories, or type of media upon which memory is stored.

Moreover, as disclosed herein, the term “storage medium” may representone or more memories for storing data, including read only memory (ROM),random access memory (RAM), magnetic RAM, core memory, magnetic diskstorage mediums, optical storage mediums, flash memory devices and/orother machine readable mediums for storing information. The term“machine-readable medium” includes, but is not limited to portable orfixed storage devices, optical storage devices, wireless channels,and/or various other storage mediums capable of storing that include orcarry instruction(s) and/or data.

While the principles of the disclosure have been described above inconnection with specific apparatuses and methods, it is to be clearlyunderstood that this description is made only by way of example and notas limitation on the scope of the disclosure.

The specific details of particular embodiments may be combined in anysuitable manner without departing from the spirit and scope ofembodiments. However, other embodiments may be directed to specificembodiments relating to each individual aspect, or specific combinationsof these individual aspects.

The above description of exemplary embodiments has been presented forthe purposes of illustration and description. It is not intended to beexhaustive or to limit to the precise form described, and manymodifications and variations are possible in light of the teachingabove.

The embodiments were chosen and described in order to explain theprinciples of the invention and practical applications to thereby enableothers skilled in the art to best utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated.

Also, it is noted that the embodiments may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc.

A recitation of “a”, “an”, or “the” is intended to mean “one or more”unless specifically indicated to the contrary.

All patents, patent applications, publications, and descriptionsmentioned here are incorporated by reference in their entirety for allpurposes. None is admitted to be prior art.

What is claimed is:
 1. A method for calibrating a camera system, themethod comprising: placing a first camera unit in an area; placing asecond camera unit in the area, wherein the first camera unit isseparated from the second camera unit by at least 10 feet and less than500 feet; acquiring, using the first camera unit, a first sequence ofimages of a target moving in the area; acquiring, using the secondcamera unit, a second sequence of images of the target moving in thearea, wherein images of the first sequence of images are related by timeto images of the second sequence of images; calculating a position andan orientation of the second camera unit relative to the first cameraunit, after acquiring the first sequence of images and the secondsequence of images, based on the first sequence of images of the targetand the second sequence of images of the target; identifying two or morepoints in the first sequence of images and in the second sequence ofimages, wherein the two or more points correspond to points in a model;calculating a position and an orientation of the first camera unitrelative to the model based on identification of the two or more pointsin the first sequence of images and in the second sequence of images;and recalculating the position and/or the orientation of the firstcamera unit relative to the second camera unit and/or the model based ondetecting movement of the first camera unit, wherein: the positionand/or the orientation of the first camera unit relative to the secondcamera unit and/or the model is recalculated after calculating theposition and the orientation of the second camera unit relative to thefirst camera unit, and the position and/or the orientation of the firstcamera unit relative to the second camera unit and/or the model isrecalculated based on detecting a background shift using images acquiredby the first camera unit.
 2. The method of claim 1, wherein calculatinga position and orientation of the first camera unit relative to themodel is performed after calculating a position and an orientation ofthe second camera unit relative to the first camera unit.
 3. The methodof claim 1, further comprising moving the target in the area, whereinthe first camera unit is stationary while acquiring the first sequenceof images of the target and the second camera unit is stationary whileacquiring the second sequence of images of the target.
 4. The method ofclaim 1, wherein: the target is a first target, the first sequence ofimages and the second sequence of images include images of a secondtarget, and the method further comprises calculating the position andthe orientation of the second camera unit relative to the first cameraunit further based on the first sequence of images of the second targetand the second sequence of images of the second target.
 5. The method ofclaim 1, wherein: a number of calculated positions of the target used incalculating the position and the orientation of the second camera unitrelative to the first camera unit is between 100 and 10,000, and thenumber of calculated positions correspond to a number of frames used inthe first sequence of images and the number of frames used in the secondsequence of images used to calculate the position and the orientation ofthe second camera unit relative to the first camera unit.
 6. The methodof claim 1, further comprising transmitting positions and/ororientations of objects to a display, wherein the display is a monitor;and/or part of a hand-held device, a head-mount device, a helmet-mountdevice, or glasses.
 7. The method of claim 5, further comprisingdisplaying to a user the number of calculated positions of the target asthe calculated positions are made.
 8. The method of claim 7, whereindisplaying to the user the number of calculated positions of the targetchanges in color and/or style based on the number of calculatedpositions.
 9. A system for calibrating camera units, the systemcomprising: a first camera unit; a second camera unit; a target; and oneor more processors configured to: acquire a first sequence of images ofthe target using the first camera unit, acquire a second sequence ofimages of the target using the second camera unit while the secondcamera unit is separated from the first camera unit by at least 10 feetand less than 50 feet, wherein images of the first sequence of imagesare related in time to images of the second sequence of images, andcalculate a relative position of the second camera unit in relation tothe first camera unit, after acquiring the first sequence of images andthe second sequence of images, based on the first sequence of images ofthe target and the second sequence of images of the target; wherein: anumber of calculated positions of the target used in calculating therelative position of the second camera unit relative to the first cameraunit is between 100 and 10,000, and the number of calculated positionscorrespond to a number of frames used in the first sequence of imagesand the number of frames used in the second sequence of images used tocalculate the relative position of the second camera unit relative tothe first camera unit.
 10. The system of claim 9, wherein the one ormore processors are further configured to: identify two or more pointsin the first sequence of images and in the second sequence of images,wherein the two or more points correspond to points in a model, andcalculate a position and an orientation of the first camera unitrelative to the model based on the first sequence of images of thetarget, the second sequence of images of the target, and identificationof the two or more points in the first sequence of images and/or in thesecond sequence of images.
 11. The system of claim 9, furthercomprising: a third camera unit configured to acquire a third sequenceof images of the target; a fourth camera unit configured to acquire afourth sequence of images of the target; and the one or more processorsare configured to: calculate a position and an orientation of the thirdcamera unit with respect to the first camera unit based on the firstsequence of images of the target and the third sequence of images of thetarget, and calculate a position and an orientation of the fourth cameraunit with respect to the first camera unit based on the first sequenceof images of the target and the fourth sequence of images of the target.12. The system of claim 9, wherein the first camera unit comprises threeimage sensors, and each image sensor of the three image sensors has adifferent orientation angle.
 13. The system of claim 9, wherein thetarget is a stick with markings.
 14. The system of claim 9, wherein theone or more processors are configured to: identify two or more points inan area on the first sequence of images and/or on the second sequence ofimages, wherein the two or more points correspond to points in a modelof the area, and calculate a position and an orientation of the firstcamera unit in relation to the model based on identifying the two ormore points in the first sequence of images and/or in the secondsequence of images.
 15. The system of claim 9, further comprising adisplay configured to display positions and/or orientations of objectsto a user.
 16. A memory device having instructions that when executedcause one or more processors to perform the following steps: acquiring afirst sequence of images of a target moving in an area from a firstcamera unit; acquiring a second sequence of images of the target movingin the area from a second camera unit while the second camera unit isseparated from the first camera unit by at least 10 feet and less than500 feet, wherein images of the first sequence of images are related bytime to images of the second sequence of images; and calculating aposition and an orientation of the second camera unit relative to thefirst camera unit, after acquiring the first sequence of images and thesecond sequence of images, based on the first sequence of images of thetarget and the second sequence of images of the target, wherein: anumber of calculated positions of the target used in calculating theposition and the orientation of the second camera unit relative to thefirst camera unit is between 100 and 10,000, and the number ofcalculated positions correspond to a number of frames used in the firstsequence of images and the number of frames used in the second sequenceof images used to calculate the position and the orientation of thesecond camera unit relative to the first camera unit.
 17. The memorydevice of claim 16, wherein the instructions further cause the one ormore processors to transmit positions and/or orientations of objects toa display, wherein the display is a monitor; and/or part of a hand-helddevice, a head-mount device, a helmet-mount device, or glasses.
 18. Thememory device of claim 16, wherein the target is a stick with markingsof known dimensions.
 19. The memory device of claim 16, wherein thefirst camera unit comprises three image sensors, and each image sensorof the three image sensors has a different orientation.
 20. The memorydevice of claim 16 having instructions that when executed cause one ormore processors to further perform the following step: recalculating theposition and/or the orientation of the first camera unit based ondetecting movement of the first camera unit, wherein: the positionand/or the orientation of the first camera unit is recalculated aftercalculating the position and the orientation of the second camera unitrelative to the first camera unit, and the position and/or theorientation of the first camera unit is recalculated based on detectinga background shift using images acquired by the first camera unit.